Introduction: Relapse prevention (RP) programs mainly focus on patients; however a patient’s workplace and communications with colleagues can also play an important role in RP. This research was conducted to assess the effectiveness of ex-addicts' Peer-Supported Vocational Network (PVN) on retention.Methods: A retrospective case-control study was conducted among PVN members (n=85) and substance users discharging from mid-term residential treatment centers (n=85) in Tehran, Iran. Case and control groups were matched for age, age of first use, duration of substance use and date of registration in treatment center or PVN. Rapid addiction tests were conducted for data collection and Chi-square and U Mann-Whitney was used for data analysis.Results: The majority of participants were single (44.1%) and 31-40 year old.(48.2%) The results indicated that there was a significant difference between case and control group in retention and abstinence duration. The case group reported four time more abstinence duration.Conclusions: PVN was an effective method for reducing the triggers in workplace and RP among substance users. Conducting the cost-effectiveness and clinical trial studies are suggested for more research.